The present invention is related to the field of electronic usemeters which develop and then display a signal magnitude representative of all total accumulated use of an apparatus. More particularly, the present invention is directed to apparatus for presetting such electronic usemeters, especially when such usemeters correspond to vehicle mileage odometers.
Typically mechanical usemeters have been utilized for keeping track of vehicle mileage (odometers), elapsed time use of mechanical equipment (hourmeters) and counting the number of revolutions of an engine crankshaft or a motor drive shaft. Such mechanical usemeters are subject to wear and therefore electronic usemeters have been developed. In addition, typically the resetting or readjusting of the mechanical usemeters is intentionally made difficult so as to prevent fraudulent tampering such as resetting an odometer to convince a used car buyer that a vehicle has been driven only rarely and only for short distances. Typically to preset or reset mechanical vehicle odometers they are either disassembled and the individual plastic "wheels" reorientated and assembled again or the drive cable to the odometer is rapidly rotated in the reverse direction to readjust the odometer reading.
It should be noted that usemeters which provide a display of total accumulated use are generally not made presettable so as to preserve the integrity of the amount of use displayed. These usemeters differ from elapsed usemeters which are readily resettable but only provide a display indicative of the amount of use between resets of the meter rather than a display indicative of total accumulated use of an apparatus. Vehicle odometers are an example of such total usemeters while vehicle trip mileage computer apparatus is an example of an elapsed usemeter.
Electronic odometers have been developed which respond to vehicle wheel rotation pulses and provide an incremented count signal related to actual travel. Since a main function of an odometer is to permanently retain a record of the total accumulated travel of the vehicle, the odometer information is stored either by constantly maintaining battery voltage to an electronic signal memory storage apparatus (volatile memory) or by storing the odometer count signal information in a non-volatile memory. The term "non-volatile" is used herein to describe an electronic signal storage apparatus which does not require the constant application of power in order to maintain stored information. When an odometer uses non-volatile storage, odometer information is typically maintained in a volatile memory in a computer, incremented in accordance with vehicle wheel rotation pulses and selectively transterred to a non-volatile memory each time the ignition switch is turned off or each time a predetermined number of miles have been traveled. Typically non-volatile memories are preferred for odometers since disconnection of the vehicle battery could result in permanent loss of odometer information in any volatile information storage system which requires the continued application of battery power to maintain the information.
Non-volatile memory odometers are typically more reliable than mechanical odometers due to their lack of mechanical parts which may wear out. Typically it is necessary to intentionally make difficult the ready adjustment of the stored odometer information in such electronic odometers to prevent unauthorized tampering with the proper mileage information. Thus after installation of the odometer generally no way is provided to adjust the odometer reading except by doing so in accordance with the normally received wheel rotation pulses. However, in certain instances it is desirable to permit some minor readjustment of the electronic odometer for automobile manufacturer factory "test drives" so that the odometer will not register these short mileage drives that are necessary to properly test the new automobile. Thus providing for a limited amount of adjustment, but not permitting unlimited adjustment of the odometer mileage is desirable, but this feature has not been provided by known electronic odometers.
In addition, in the event of the failure of an electronic odometer, it is desirable to replace the electronic odometer with a new electronic odometer having a reading preset to the estimated total actual mileage of the vehicle in which the new odometer will be installed. In present available electronic odometers this is accomplished by presetting the replacement odometer at the factory and then permanently tagging or coding the odometer so as to identify it as a substitute device to thereby put the owner of the vehicle on notice that this is a substitute odometer and not an original equipment odometer. This complicates and delays the obtaining of a substitute or replacement odometer since the adjustment of the odometer mileage will take place at the factory. In addition, this adjustment of the odometer at the factory requires special equipment. It would be more desirable to have this adjustment take place during the installation of the replacement odometer while still providing the above mentioned safeguards of preventing unlimited further adjustment while also identifying the substitute odometer as a replacement item.